Hydrazine decomposition process using metal promoters

ABSTRACT

The use of metal powders as synergistic promoters for solid oxidizing agents (initiators) for gas generators.

United States Patent Hubbuch et al.

[451 June 6,1972

HYDRAZINE DECOMPOSITION PROCESS USING METAL PROMOTERS Inventors: Theodore N. Hubbuch, Florence; James A. Murfree, Jr.; William A. Duncan, both of Huntsville; Billy J. Sandlin, Athens; Henry A. Nappier, Laceys Spring, all of Ala.

Assignee: The United States of America as represented by the Secretary of the Army Filed: July 5, 1967 Appl. No.: 651,323

U.S. Cl..'. ..60/2l8, 60/219, 60/220,

149/36 Int. Cl. ..C06d 5/04, C06d 5/10 Field of Search ..60/218, 219, 220; 149/36 6/1966 Kaufman .....60/220 7/1967 Kaufman ..60/220 Primary Examiner-Benjamin R. Padgett Attorney-Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and Elihu L. Turetsky ABSTRACT The use of metal powders as synergistic promoters for solid oxidizing agents (initiators) for gas generators.

5 Claims, No Drawings HYDRAZINE DECOMPOSITION PROCESS USING METAL PROMOTERS BACKGROUND OF THE INVENTION There is considerable interest in the rocket propulsion industry in the development and use of liquid monopropellant gas generators.- Although the majority of work in this field has been in catalytic decomposition schemes, recent attention has been focused on schemes of gas generation utilizing a liquid mono-propellant with an initiator and an inert porous bed or support as more particularly disclosed in copending application Ser. No. 651,654, filed July 5, 1967. In these schemes, the monopropellant reacts with the initiator to start decomposition, generate heat, and heat the support which, when heated, thermally sustains the decomposition. Applicants have learned that this gas generation scheme can be improved by using metal powders as synergistic promoters.

Accordingly, the principal object of this invention is to provide a gas generation scheme that utilizes metal powders as synergistic promoters.

Another object of this invention is to improve the buming rates and lower the ignition delay in propellant decompositions using a liquid monopropellant.

SUMMARY OF THE INVENTION In accordance with this invention, it has been discovered that bringing hydrazine into contact with a dry mixture of aluminum powder and potassium permanganate results in a rapid and vigorous chemical reaction releasing heat and light.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A dry mixture of aluminum powder and potassium permanganate and similar mixtures of metals and oxidizing agents are used as initiators in gas generators utilizing hydrazine and similar fuels which undergo exothermal decomposition to release gas. Although almost any type of exothermally decomposing fuel may be used, the monopropellant must be of an exothcrmally decomposing type so that when decomposed, it liberates heat which raises the temperature of the absorbing material or bed such that the exotherrnal decomposition of the monopropellant is maintained thermally even after the oxidizing agent has been consumed.

The mixture is incorporated in a suitable carrier bed made of an inert porous support material such as porous firebrick. Thus, when the monopropellant enters the carrier bed, the rapid vigorous reaction between the monopropellant and the mixture (incorporated in the bed) heats the bed to a temperature sufficient to maintain the exotherrnal decomposition of the monopropellant after the metal powder and oxidizing agent are expended.

The finely divided metal powder may be manganese, aluminum, zinc or iron, and mixtures thereof. Thermit (trademark for an equal mixture by weight of ferric oxide and powdered metallic aluminum) and other iron oxide and aluminum mixtures are especially desirable.

The oxidizing agent is a finely divided inorganic oxidizing salt. Preferably, the anion portion of said salt is permanganate, iodate, dichromate or hyperchlorite. Of course, mixtures thereof may be employed.

The proportion of the finely divided metal powder in the intimate mixture of the metal and oxidizing agent should be from about 10 percent to about 30 percent by weight. Preferably, for best results, it should be about 20 percent.

The exotherrnally decomposing monopropellant in the propellant composition is preferably hydrazine or a hydrazinetype (e.g. monomethylhydrazine or l,l-dimethylhydrazine) fuel. Mixtures thereof may also be desirable. The monopropellant must be exotherrnally decomposing to sustain the reaction after the metal powder and oxidizing agent are expended. Note, however, that although almost any type of exothermally decomposing monopropellant may be used, not every oxidizing agent mentioned above will work with every exothermally decomposing monopropellant. In particular, tassium permanganate will not work with l, l-dirnethyl ydrazine. Accordingly, the tenn suitable oxidizing agent is defined herein to mean a workable oxidizing agent for the particular monopropellant chosen.

Various other modifications and variations of this invention may be employed by those skilled in the art in the light of the above teachings, which modifications and variations are still within the spirit and scope of this invenu'on.

We claim:

1. The process of gas generation comprising: providing an inert porous support material; supporting a mixture of inorganic oxidizing agent and finely divided metal powder in said inert porous support material, said oxidizing agent being a finely divided salt, said salt having as its anion portion permanganate, iodate, dichromate or hyperchlorite, said metal powder being manganese, magnesium, aluminum, zinc or iron; and, bringing an exothermally decomposing monopropellant selected from hydrazine, monomethylhydrazine or l,ldimethyhydrazine into contact with said inert porous support material and said mixture to cause said monopropellant and said mixture to react with the liberation of heat and gas and thereby heat said inert porous support material to a temperature sufficient to maintain decomposition of said monopropellant afier said suitable oxidizing agent and said metal powder are expended.

2. The process of claim 1 wherein said monopropellant is hydrazine or monomethylhydrazine.

3. The process of claim 1 wherein said suitable oxidizing agent is a finely divided salt, said salt having as its anion portion iodate, dichromate or hyperchlorite.

4. The process of claim 3 wherein said metal powder comprises from about 10 percent to about 30 percent by weight of said mixture.

5. The process of claim 4 wherein said metal powder comprises about 20 percent by weight of said mixture. 

2. The process of claim 1 wherein said monopropellant is hydrazine or monomethylhydrazine.
 3. The process of claim 1 wherein said suitable oxidizing agent is a finely divided salt, said salt having as its anion portion iodate, dichromate or hyperchlorite.
 4. The process of claim 3 wherein said metal powder comprises from about 10 percent to about 30 percent by weight of said mixture.
 5. The process of claim 4 wherein said metal powder comprises about 20 percent by weight of said mixture. 